Most swimming pools, both in-ground, and above ground, are provided with a system for recirculating water the function of which is to recover water contained in the swimming pool, send it to a filtration system, disinfect it and then introduce it again into the swimming pool itself. One of such systems, the so called water overflow edge system, is provided with a pump system that draws water from a compensation tank and reintroduces it inside the swimming pool through inlet fittings arranged on the vertical walls or on the bottom of the swimming pool itself.
The swimming pool is provided with a total or partial peripheral channel, in which water overflows or, in other words, pours out passing over the upper edge of the vertical walls of the swimming pool itself. The water that overflows into the peripheral channel flows by gravity towards a plurality of discharge outlets, also known as “drains”, usually arranged at the bottom of the channel or in any case in a low position. From the drains, through piping connected to them and with suitable collectors, the water reaches the compensation tank. The compensation tank, in addition to being used for containing the water reserve that is necessary for supplying the pumps of the filtration system when there are no users in the swimming pool, is also used for storing the volume of water corresponding to that which overflows into the peripheral channel consequently to the entrance in the swimming pool of possible users.
In prefabricated swimming pools of the conventional type, usually built in metal and coated with a plastic membrane (typically PVC), the peripheral channel of the water overflow edge is in general entirely made with the same material which forms the walls of the swimming pool, that is to say metal coated with a plastic membrane. The peripheral channel is usually shaped in a complex manner, with a section that often also has two steps on the opposite vertical sides. These steps are intended for supporting a walking grid that for safety reasons covers the peripheral channel.
This type of peripheral channel for a water overflow edge is particularly complex and costly due to the numerous folds to be made in the metal during production. It is consequently difficult to build swimming pools with walls having curves, that is to say not rectilinear. A curved water overflow edge cannot indeed be made with channels formed by a single sheet of metal. A curved water overflow edge does, on the other hand, require many components that are suitably shaped to be assembled, with a high chance of water leaking due to the presence of numerous joints in the metal structure.
Water overflow edges have therefore been made for swimming pools in which the peripheral channel is provided with modular structural elements manufactured with materials other than metal. Embodiments of a similar water overflow edge are described, for example, in patent IT 1374335 to the same Applicant, as well as in documents EP 1 518 975 A1 and U.S. Pat. No. 4,235,008 A. This water overflow edge comprises a channel that, at the front, consists of a plurality of structural elements made of ceramic material, which are configured for coupling with one another “end-to-end” and for being, at the bottom, fixed to the bottom of the channel and/or to the inner wall of the swimming pool. On each structural element made of ceramic material there is thus a support portion that is obtained for supporting the walking grid.
Also this second type of peripheral channel for a water overflow edge is not without drawbacks, in particular concerning the structural element made of ceramic material. Following the production of numerous structural elements in ceramic material, as well as multiple installations of peripheral channels comprising such structural elements, in swimming pools of various kinds, the following problems were found:                difficulty in making the structural element in ceramic material, since it is massive and heavy;        a reduced dimensional stability of the structural element in ceramic material following the relative extrusion process, due to its great weight;        the possibility of deformation of the structural element in ceramic material in its drying phase;        long and energy-consuming drying for the conspicuous mass of the structural element in ceramic material;        difficulty for the structural element in ceramic material to completely dry, with the occurrence in its central core of the phenomenon called in jargon “black core”;        the possibility of high absorption of humidity by the peripheral channel, with a consequent reduction of the anti-freeze properties or, in other words, resistance to the frost disintegrating action;        high percentage of waste and high cost.        